Belt tensioner

ABSTRACT

A tensioner for a power transmission belt that is adapted to be operated in an endless path is provided and comprises a support unit for being fixed relative to the belt, a belt engaging unit carried by the support unit and being movable relative thereto, a mechanical spring unit operatively associated with the support unit and the belt engaging unit for urging the belt engaging unit relative to the support unit and against the belt with a force to tension the belt, and a fluid dampening unit operatively associated with the support unit and the belt engaging unit to dampen the movement of the belt engaging unit relative to the support unit in at least one direction of the movement thereof, the fluid dampening unit comprising a piston and cylinder unit. The mechanical spring unit comprises a pair of coiled compression springs with their longitudinal axes disposed in substantially parallel side-by-side spaced relation, the fluid dampening unit being generally disposed between the springs and in substantially parallel relation therewith.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional patent application of its copendingparent patent application, Ser. No. 301,351, filed Sept. 11, 1981, nowU.S. Pat. No. 4,413,982.

BACKGROUND OF THE INVENTION

B 1. Field of the Invention

This invention relates to an improved tensioner for an endless powertransmission belt or the like, an improved part for such a tensioner orthe like and to methods of making such a tensioner and/or part therefor.

2. Prior Art Statement

It is known to applicant to provide a tensioner for a power transmissionbelt that is adapted to be operated in an endless path, the tensionercomprising a support means for being fixed relative to the belt, a beltengaging means carried by the support means and being movable relativethereto, mechanical spring means operatively associated with the supportmeans and the belt engaging means for urging the belt engaging meansrelative to the support means and against the belt with a force totension the belt, and a fluid dampening means operatively associatedwith the support means and the belt engaging means to dampen themovement of the belt engaging means relative to the support means in atleast one direction of movement thereof, the fluid dampening meanscomprising a piston and cylinder means;

For example, see the copending patent application Ser. No. 296,694,filed Aug. 27, 1981, of Leslie B. Wilson, wherein the fluid dampeningmeans comprises a cylinder means having a piston means therein anddefining two chambers for fluid in the cylinder means on opposite sidesof the piston means together with preferential flow control meansinterconnecting the two chambers together.

Also see the copending patent application Ser. No. 296,697, filed Aug.27, 1981, of Randy C. Foster et al wherein another such tensioner isprovided and the fluid dampening means thereof comprises a cylindermeans having a piston means therein and defining two chambers for fluidin the cylinder means on opposite sides of the piston means with thespring means being disposed in one of those chambers.

Also see the U.S. Pat. No. 3,802,286 of Gerhard Winklhofer et al whereina piston of a piston and cylinder means of a tensioner is urged in atensioning direction by a compression spring disposed within thecylinder and bearing against the piston member, the piston member beingcup-shaped and the cylinder member being cup-shaped with the pistonmember telescoped therein and with the cavity therebetween being filledwith a hydraulic fluid for movement dampening purposes.

It is also known to provide a belt tensioner with a friction surfacedampening means of the solid type utilized to tend to dampen vibrationsand the like that are imposed on the belt tensioner.

It is also known to provide fluid couplings, such as torque converters,wherein rotational movement of one member causes rotational movement ofanother member because a fluid translates such movement between the twomembers, each member having vanes thereon.

SUMMARY OF THE INVENTION

It is one feature of this invention to provide an improved tensioner fora power transmission belt or the like.

In particular, it was found according to the teachings of this inventionthat a relatively small and compact belt tensioner could be provided byuniquely arranging the mechanical spring means thereof and the fluiddampening means thereof in a manner believed to be more compact than thearrangements set forth in the aforementioned copending patentapplications, Ser. No. 296,694, filed Aug. 27, 1981, of Leslie B. Wilsonand Ser. No. 296,697, filed Aug. 27, 1981, of Randy C. Foster et al,both of these copending patent applications being hereby incorporatedinto this disclosure by this reference thereto.

In particular, it was found according to the teachings of this inventionthat the spring means of a belt tensioner can comprise a pair of springsdisposed in substantially parallel spaced relation with the fluiddampening means having at least a part thereof disposed between thesprings in substantially parallel relation therewith to render the belttensioner substantially small and compact.

For example, one embodiment of this invention provides a tensioner for apower transmission belt that is adapted to be operated in an endlesspath, the tensioner comprising a support means for being fixed relativeto the belt, a belt engaging means carried by the support means andbeing movable relative thereto, mechanical spring means operativelyassociated with the support means and the belt engaging means for urgingthe belt engaging means relative to the support means and against thebelt with a force to tension the belt, and a fluid dampening meansoperatively associated with the support means and the belt engagingmeans to dampen the movement of the belt engaging means relative to thesupport means in at least one direction of movement thereof the fluiddampening means comprising a piston and cylinder means and, themechanical spring means comprising a pair of coiled compression springswith their longitudinal axes disposed in substantially parallelside-by-side spaced relation with the fluid dampening means side-by-sidebeing generally disposed between the springs and in substantiallyparallel relation therewith. The belt engaging means has a part thereofdisposed in sliding relation with the support means, the part of thebelt engaging means having a pair of substantially flat parallel spacedapart surfaces interconnected together by a front wall. The supportmeans has a pair of substantially flat parallel spaced apart surfacesrespectively facing the surfaces of the part of the belt engaging meansand being interconnected together by a rear wall. Bearing means aredisposed between the facing surfaces to facilitate the sliding movementbetween the part of the belt engaging means and the support means. Thepart of the belt engaging means has a third substantially flat surfacedisposed between the pair of surfaces thereof and being substantiallytransverse relative thereto, the springs and the piston member of thefluid dampening means being respectively operatively interconnected tothe third surface of the belt engaging means. The part of the supportmeans has a third substantially flat surface disposed between said pairof surfaces thereof and being substantially transverse thereto and beingbetween the pair of springs. The cylinder member of the fluid dampeningmeans being operatively interconnected to the third surface of thesupport means.

Accordingly, it is an object of this invention to provide an improvedtensioner for a power transmission belt or the like that is adapted tobe operated in an endless path, the tensioner of this invention havingone or more of the novel features of this invention as set forth aboveor hereinafter shown or described.

Other objects, uses and advantages of this invention are apparent from areading of this description which proceeds with reference to theaccompanying drawings forming a part thereof and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary isometric view looking toward the front end ofan automobile engine which utilizes one embodiment of the belt tensionerof this invention.

FIG. 2 is a view looking perpendicularly toward th front end of theautomobile engine of FIG. 1.

FIG. 3 is an enlarged front view, partially broken away and partially incross section, of the belt tensioner of this invention that is beingutilized for tensioning the power transmission belt of FIGS. 1 and 2.

FIG. 4 is a cross-sectional view taken on lines 4--4 of FIG. 3.

FIG. 5 is a cross-sectional view taken on lines 5--5 of FIG. 3.

FIG. 6 is an exploded perspective view of the various parts forming thebelt tensioner of FIGS. 3-5.

FIG. 7 is a schematic view in cross section and illustrates the fluidflow control means of the fluid dampening means of the belt tensioner ofFIGS. 3-6.

FIG. 8 is a view similar to FIG. 3 and illustrates another embodiment ofthe belt tensioner of this invention.

FIG. 9 is a view similar to FIG. 8 and illustrates another embodiment ofthe belt tensioner of this invention.

FIG. 10 is a side view of the belt tensioner of FIG. 9 and is taken inthe direction of the arrows 10--10 thereof.

FIG. 11 is a cross-sectional view of the fluid dampening means of thebelt tensioner of FIGS. 9 and 10 and is taken on lines 11--11 of FIG.10.

FIG. 12 is an exploded perspective view illustrating the parts of thefluid dampening means of the belt tensioner of FIGS. 9 and 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the various features of this invention are hereinafter illustratedand described as providing a belt tensioner for a particular powertransmission belt of a particular motor vehicle engine, it is to beunderstood that the various features of this invention can be utilizedsingly or in any combination thereof to provide a belt tensioner forother arrangments as desired.

Also, while the improved rotary dampening means of this invention isdescribed and illustrated as providing part of a belt tensioner, it isto be understood that the improved rotary dampening means of thisinvention can be utilized for other purposes as desired.

Therefore, this invention is not to be limited to only the embodimentsillustrated in the drawings, because the drawings are merely utilized toillustrate one of the wide variety of uses of this invention.

Referring now to FIGS. 1 and 2, an automobile engine is generallyindicated by the reference numeral 20 and utilizes an endless powertransmission belt 21 for driving a plurality of driven accessories ashereinafter set forth, the improved belt tensioner of this inventionbeing generally indicated by the reference numeral 22 and being utilizedto provide a tensioning force on the belt 21 in a manner hereinafter setforth.

The endless power transmission belt 21 may be of any suitable type knownin the art and is preferably made primarily of a polymeric materialbecause the unique features of the tensioner 22 of this inventionreadily permits the tensioner 21 to tension a belt having a polyesterload-carrying cord in an efficient manner as hereinafter described.

The belt 21 is driven by a driving sheave 23 which is operativelyinterconnected to the crankshaft of the enging 20 in a manner well knownin the art. The driving sheave 23 drives the belt 21 in an endless pathand thereby drives a sheave 24 of a power steering device used in anautomobile (not shown) utilizing the engine 20, a sheave 25 of an enginewater pump, a sheave 26 of an air pump of a type used in anantipollution system for the engine 20, a sheave 27 of an engineelectrical alternator 28, and a sheave 30 of a compressor 31 of an airconditioning system for the automobile utilizing the engine 20.

All of the driven accessories, through their sheaves 24, 25, 26, 27 and30, impose a load on the belt 21. However, only the detailed descriptionof the load being imposed by the compressor 31 and its sheave 30 on thebelt 21 will be hereinafter described inasmuch as such load is generallyof a comparatively high magnitude.

In particular, the compressor 31, upon being driven, creates a slackside 33 and a tight side 34 in the belt 21 upon turning on of the airconditioner system in the automobile, the slack side 33 and tight side34 being produced since the belt is rotating clockwise as indicated bythe arrow 35 in FIGS. 1 and 2.

The belt tight side 34 (and hence, slack side 33) varies in tightness,i.e., magnitude of tightness, in a cyclic manner and as a function ofthe inherent cyclic change in the loads imposed by the compressor 31.This cylic change and load varies between greater extremes inapplications where the compressor 31 is of a piston type. The cyclicload imposed by the compressor 31 has a tendency to cause the slack side33 of the belt 21 to vibrate or oscillate.

In addition to such vibrations and oscillations of the belt 21, it isknown that normal belt wear and heat variations in the enginecompartment for the engine 20 produce variations in the length of thebelt 21 that require compensation for the same.

Thus, it is known that it is difficult to maintain such a belt 21 undertension with a force required to insure non-slipping engagement anddriving of the driven sheaves whereby numerous belt tensioners have beenproposed and used heretofore in an effort to provide the requiredtension.

It is believed that the improved belt tensioner 22 of this inventionfunctions in a manner to provide a proper tensioning force on the belt21 to overcome the aforementioned problems, namely, provides therequired tension in the overall belt 21 as well as prevents any tendencyof the belt to oscillate in an undesirable manner as a result of thecyclic load change imposed by the compressor 31 whereby the improvedbelt tensioner 22 of this invention will now be described.

As best illustrated in FIGS. 3 and 6, the improved belt tensioner 22 ofthis invention comprises a support means 36 adapted to be fixed to amounting bracket 37 of the engine 20 as illustrated in FIGS. 1 and 2. Abelt engaging means that is generally indicated by the reference numeral38 is movably carried by the support means 36 in a manner hereinafterset forth. The tensioner 22 has mechanical spring means that isgenerally indicated by the reference numeral 39 operatively associatedwith the support means 36 and belt engaging means 38 to tend to urge thebelt engaging means 38 against the slack side 33 of the belt 21 insubstantially a true vertically downwardly direction in a manner tosubstantially bisect the angle made by the belt 21 between the sheaves27 and 30 as illustrated in FIG. 2.

The belt tensioner 22 also includes a fluid dampening means that isgenerally indicated by the reference numeral 40 and is operativelyassociated with the support means 36 and the belt engaging means 38 todampen movement of the belt engaging means 38 relative to the supportmeans 36 in a manner hereinafter set forth.

The belt engaging means 38 comprises an idler pulley 41 rotatablymounted on an axle 42 carried by a slide member 43 disposed for slidingin a box-like member 44 of the support means 36 in a manner hereinafterset forth, the slide member 43 having a substantially rectangular frontwall 45 and a pair of rearwardly extending substantially parallelrectangular and integral side walls 46 and 47 being bridged by atransverse wall 48 secured thereto in any suitable manner, such as bywelding on the like. In this manner, the rearwardly extending side walls46 and 47 define a pair of outwardly facing substantially parallelsurfaces 49 and 50 while the transverse wall 48 defines a surface 51that is disposed between and transverse to the side surfaces 48 and 50for a purpose hereinafter described.

The box-like member 44 of the support means 36 has a substantiallyrectangular rear wall 52 with a pair of forwardly extending parallel andintegral side walls 53 and 54 which respectively define inwardly facingsubstantially parallel surfaces 55 and 56 for respectively facing theside surfaces 49 and 50 of the slide member 43 of the belt engagingmeans 38 for a purpose that will be apparent hereinafter.

A substantially rectangular bottom wall 57 is secured to the rear wall52 and side walls 53 and 54 of the support member 44 in any suitablemanner, such as by welding or the like, and a substantially rectangulartop wall 58 is likewise secured to the rear wall 52 and side walls 53 inany suitable manner, such as by welding or the like. In addition apartial substantially rectangular front wall 59 and partial side walls60 and 61 are carried by the top wall 58 and extend across and overlapthe side walls 53 and 54 in a cap-like manner as illustrated in FIGS. 3and 4 to provide a means for capturing and guiding up and down movementof a pair of substantially rectangular spring retainers 62 whichrespectively have threaded openings 64 passing therethrough andrespectively threadedly receiving threaded adjusting members 65 that arerotatably carried in openings 66 in the top wall 58.

In particular, each threaded adjusting member 65 has a reducednon-threaded section 67 intermediate the threaded portion 68 thereof andan enlarged head 69 thereof that is telescopically received in anopening 66 of the top wall 58 and is held therein by a C-shaped clip 70in a manner well known in the art so that rotation of the particularthreaded fastening member 65, such as by turning the head 69 thereofwith a suitable tool or the like, will cause rotation of the adjustingmember 65 and, thus, a threading relation of its respective springretainer 62 upwardly or downwardly on the threaded fastening member 65within the top cap portion of the box-like support member 44 for apurpose hereinafter described.

The facing side surfaces 55 and 56 of the box-like support member 44respectively are provided with a pair of parallel grooves 71 thatrespectively extend from openings 72 formed through the respective sidewall 53 or 54 to the ends 73 thereof.

In a similar manner the outwardly facing side surfaces 49 and 50 of theslide member 43 of the belt engaging means 38 each has a pair ofparallel grooves 74 formed therein with each groove 74 terminating atthe opposed ends 75 and 76 thereof.

The grooves 74 of the slide member 43 cooperate with the grooves 71 ofthe support member 44 to carry bearing means that are generallyindicated by the reference numeral 77 and that facilitate slidingmovement of the slide member 43 relative to the support member 44.

In particular, the bearing means 77 comprise a plurality of ballbearings 78 that substantially fill the grooves 74 of the slide member43 and partially fill the grooves 77 of the support member 44 to permitup and down sliding movement of the slide member 43 within the box-likemember 44 as illustrated in FIGS. 3 and 4.

In order to initially dispose the ball bearings 78 in the cooperatinggrooves 71, 74, the slide member 43 is positioned in the member 44 sothat the upper ends 74 of the grooves 74 are slightly above the openings72 in the side walls 53 and 54 of the member 44 so that the ballbearings 78 can be fed through the openings 72 into the cooperatinggrooves 71 and 74. Once the grooves 74 have been filled with the ballbearings 78, the slide member 43 is moved downwardly so that the ends 75of the grooves 74 are below the openings 72 whereby the ball bearings 78cannot escape from the cooperating grooves 71, 74, the openings 72 beingso positioned that the normal range of up and down movement of the slidemember 43 relative to the box-like member 44 during its belt tensioningfunction of the tensioner 22 in a manner hereinafter set forth will notcause the upper ends 75 of the grooves 74 of the slide member 43 toreach the openings 72 whereby the ball bearings 78 are fully captured inthe cooperating grooves 71 and 74 for their substantially frictionlessbearing purpose.

The mechanical spring means 39 of the tensioner 22 of this inventioncomprises a pair of coiled compression springs 79 with theirlongitudinal axes disposed in spaced-apart parallel side-by-side spacedrelation in the box-like support member 44 and respectively have upperends 80 bearing against the adjustable spring retainers 62 while havingthe lower ends 81 thereof respectively being received in substantiallycylindrical recesses 82 formed in the surface 51 of the transverse wall48 of the slide member 43.

In this manner, the force of the compression springs 79 tends to urgethe slide member 43 downwardly relative to the support member 44, theforce of the compression springs 79 being adapted to be adjusted by theadjustable spring retainer 62 being axially threaded upwardly anddownwardly on the respective threaded adjusting members 65 in the mannerpreviously set forth.

The fluid dampening means 40 comprises a piston and cylinder means thatis generally indicated by the reference numeral 83 and comprises acylinder member 84 and a piston member 85, FIG. 7, disposed for movementwithin a substantially cylindrical chamber 86 formed in the cylindermember 84, the piston member 85 having a piston rod 87 secured theretoand extending from opposed sides 88 and 89 thereof so that a lower part90 of the piston rod 87 extends out of an opening 91 in a lower end wall92 of the cylinder member 84 and an upper part 93 of the piston rod 87extends out of an opening 94 in an upper end wall 95 of the cylindermember 84.

The piston member 85 of the fluid dampening means 40 has an externalperipheral surface 96 disposed in sliding and sealing engagement withthe internal peripheral surface 97 of the cylinder member 84 thatdefines the chamber 86 thereof whereby the piston member 85 divides thechamber 86 into an upper chamber section 98 and a lower chamber section99 substantially sealed from each other by the piston member 85.However, the chamber sections 98 and 99 are fluidly interconnectedtogether by a passage defining means that is generally indicated by thereference numeral 100 and comprises a conduit means 101 having one end102 thereof secured in an opening 103 formed through the cylinder member84 adjacent the end wall 95 thereof while the other end 104 of theconduit means 101 is secured in an opening 105 formed through thecylinder member 84 adjacent the end wall 92, the conduit means 101having a flow control valve means therein that is generally indicated bythe reference numeral 106 and that is utilized for controlling fluidflow through the conduit means 101 in a manner hereinafter described.

The cylinder member 84 has a pair of opposed reduced ends 107 and 108through which the piston rod parts 93 and 90 respectively extend, thereduced end 108 being externally threaded to be threadedly received inan internally threaded bore 109 of a substantially rectangular block 110secured to the rear wall 52 of the support member 44 in any suitablemanner, such as welding or the like, whereby the lower end 108 of thecylinder member 84 is secured to the support member 44 so as to benon-movable relative thereto. The upper end 107 of the cylinder member84 projects out of an opening 111 formed in the top wall 58 of thebox-like support member 44.

The piston member 85, in turn, is operatively interconnected to theslide member 43 because the lower piston rod part 90 thereof has areduced externally threaded section 112 received through an opening 113formed through the transverse wall 48 of the slide member 43 and carriesa nut 114 thereon to sandwich the transverse wall 48 between the nut 114and an annular shoulder 115 on the piston rod section 90 whereby thepiston member 85 will move in unison with the slide member 43 relativeto the support member 44 in a manner hereinafter set forth.

Thus, it can be seen that the piston and cylinder means 83 is disposedsubstantially parallel to the springs 79 and between the same, thesprings 79 and piston member 85 being operatively interconnected to theslide member 43 and the springs 79 and cylinder member 84 beingoperatively interconnected to the support means 36 and thereby permitthe tensioner 22 to be substantially small and compact to operate in amanner hereinafter set forth.

The flow control valve means 106 illustrated in FIG. 7 comprises ahousing means 116 having a first passage 117 passing therethrough anddefining opposed openings 118 and 119 in the housing means 116 thatrespectively receive ends 120 and 121 of conduit sections 122 and 123 ofthe conduit means 101 as illustrated, the conduit ends 120 and 121 beingsecured in the openings 118 and 119 in any suitable manner, such as bythe threaded relation illustrated.

A one-way check valve means that is generally indicated by the referencenumeral 124 in FIG. 7 is disposed in the first passage means 117 topermit fluid flow from the conduit section 123 to the conduit section122 and, thus, from the chamber section 99 to the chamber section 98 ofthe fluid dampening means 40 while preventing reverse flow from theconduit section 122 to the conduit section 123 through the first passage117 and, thus, from the chamber section 99 of the fluid dampening means40.

In particular, the one-way check valve means 124 comprises a movablevalve member 125 normally urged against a valve seat 126 in the passagemeans 117 by a compression spring 127 so that fluid pressure from theconduit section 123 will open the valve member 125 against the force ofthe compression spring 127 to provide full and unrestricted flow offluid from the conduit section 123 to the conduit section 122 throughthe passage means 117. However, when fluid flow is from the conduitsection 122 toward the conduit section 123 through the passage means117, the compression spring 127 closed the valve member 125 against thevalve seat 126 to prevent such fluid flow.

However, a second passage 128 is formed in the housing means 116 and isinterconnected to the passage 117 on opposite sides of the one-way checkvalve means 124 thereof so as to be in fluid communication with theconduit sections 122 and 123. The passage 128 is adapted to have theflow of fluid thereto controlled by an adjusting member 129 in a mannerwell known in the art, the adjusting member 129 having a threadedsection 130 disposed in a threaded bore 131 in the housing means 116 sothat an operator can rotate the adjusting member 129 by grasping a knobend 132 thereof so as to position the adjusting member 129 in a desiredflow restricting position thereof to limit the rate of fluid flowthrough the passage 128 and, thus, the rate of fluid flow from theconduit section 122 to the conduit section 123 through the passage 128as the one-way valve means 124 is preventing fluid flow at that timethrough the passage 117 for a purpose hereinafter described.

As previously stated, the piston rod section 90 is interconnected to thebelt engaging means 38 while the cylinder member 84 is interconnected tothe stationary support means 36 so as the belt engaging means 38 movesdownwardly in the drawings in a direction to tension the belt 21, suchdownward movement of the piston rod 87 and piston member 85 therewithtends to decrease the volume of the chamber section 99 while increasingthe volume of the chamber section 98 a like amount. However, the fluidbeing displaced from the chamber section 99 by the downwardly movingpiston 85 must be transferred to the chamber section 98 through theconduit means 101 and, thus, through the flow control valve means 106.Because the fluid flow through the passage 117 of the flow control means106 is from the conduit section 123 to the conduit section 122, theone-way check valve means 124 is opened and permits such fluid flowtherethrough in substantially an unrestricted manner.

Conversely, when the piston rod 87 is moved upwardly by the beltengaging means 38 being moved upwardly by the tensioned belt 21 in amanner hereinafter set forth, such upward movement of the piston rod 87is retarded or restricted by amount determined by the setting of theadjusting member 129 of the flow control means 106.

In particular, as the piston member 85 moves upwardly in FIG. 7, thesame tends to displace fluid from the chamber section 98 to the chambersection 99 through the passage defining means 100 and thus the fluidflow through the flow control valve means 106 is from the conduitsection 122 to the conduit section 123 whereby the one-way check valvemeans 24 closes the passage 117 so that the entire fluid flow has topass through the restricted passage 128 of the flow control valve 106and thereby restricts the upward movement of the belt engaging means 38relative to the belt 21 for a purpose hereinafter described.

While the flow control valve means 106 has been previously illustratedand described as merely restricting fluid flow in one direction thereofin an adjustable manner, it is to be understood that the flow controlvalve means 106 can be a fixed flow control valve means, be anadjustable flow control valve means in both directions of flowtherethrough and even be adapted to close the passage defining means 100to substantially lock the idler pulley 41 in a set position relative tothe support means 36 as will be apparent hereinafter.

Also, while it is presently preferred that the fluid that fills thechamber sections 98, 99 and the passage defining means 100 comprise aliquid, such as a hydraulic oil or the like, it is to be understood thatany suitable fluid, such as air or other gas or gases, can be utilizedand will function substantially in the same manner. Therefore, thedampening means 40 is referred to as a fluid dampening means.

In order to mount the tensioner 27 of this invention to the bracket 37of the engine 20, the rear wall 52 of the support member 44 has anextenrally threaded fastening member 133 secured thereto and adapted tobe received in an opening (not shown) in the bracket 37 and be securedthereto by a nut (not shown) threaded on the threaded fastening member133 in a manner well known in the art. In order to prevent rotation ofthe tensioner 22 relative to the support bracket 37, one or more rigidpins 134 can be secured to the rear wall 52 of the support member 44 andbe received in suitable openings (not shown) in the bracket 37 at thesame time the fastening member 33 is being received in its opening.However, it is to be understood that other mounting means can beutilized to secure the tensioner 22 to the bracket 37 as desired.

Therefore, it can be seen that it is a relatively simple method of thisinvention to make the improved belt tensioner 22 of this invention thatis adapted to operate in a manner now to be described.

When the tensioner 22 of this invention has been mounted by its supportmember 44 to the bracket 37 of the engine 20 in the manner previouslydescribed so that the idler pulley 41 thereof is engaging against thebelt 21 under the urging force of the springs 79, the installer canadjust the adjusting members 65 upwardly or downwardly relative to thetop plate 58 so that the springs 79 will be under a certain initialcompression and thereby be providing a predetermined force against thebelt 21 in the at rest position of the engine 20. In addition, the flowcontrol valve 106 has been either factory adjusted or installer adjustedto set the desired differential flow characteristics between thechambers 98 and 99 of the dampening means 40.

Thereafter, each time the engine 20 is initially started so as to causeslack in the slack side 33 thereof and provide a tensioning forcethereon as determined by the force of the springs 79, such inwardmovement of the pulley 41 causes the piston member 85 to move downwardlyin FIG. 7 and displace fluid in the chamber 99 through the passagedefining means 100 and the flow control valve means 106 to the chamber98 in a manner to dampen such downward movement of the pulley 41.

Thus, it can be seen that as the belt 21 is traveling in the directionof the arrow 35 in FIGS. 1 and 2 by the running engine 20, anyvibrations and oscillations of the belt 21, such as caused by theturning on and off of the air conditioning compressor 31 as previouslyset forth, will cause an up and down oscillation of the portion 33 ofthe belt 21 which movement is imposed on the pulley 41 of the tensioner22.

In those instances where the deflection of the portion 33 of the belt 21is upwardly in FIGS. 1 and 2 to tend to cause the pulley 41 to moveupwardly relative to the support means 36, such movement causes thepiston member 85 to move upwardly and thereby force the fluid from thechamber 98 through the passage defining means 100 and flow control valve106 to the chamber 99 and since the flow control valve 106 is set torestrict such flow at a greater rate than in the reverse direction offluid flow through the passage defining means 100, such upward movementof the pulley 41 relative to the support means 36 is at a slower ratethan when the pulley 41 is being moved downwardly away from the supportmeans 36, the flow control means 106 being such that even the downwardmovement of the pulley 41 away from the support means 36 is dampened toa certain degree.

In this manner, it is believed that the dampening means 40 of thisinvention will prolong the life of the tensioner 22 so that rapidoscillations of the springs 79 thereof cannot take place and the springs79 will perform their tensioning function in a relatively smooth manner.

In particular, since the flow control means 106 provides a preferentialflow ratio that can be controlled, the tensioner 22 will deliverincreased tension on the belt 21 when the belt 21 is subjected toacceleration and/or heavy cyclic loads commonly encountered in beltdrive systems. Accordingly, if the fluid flow from chamber 98 to chamber99 is more restrictive than reverse flow, load fluctuations in the beltsystem will result in an increased pressure on the top side 88 of thepiston 85 which will force the idler pulley 41 down into the belt 21 andresult in greater belt tension. In this manner, the tensioner 22 willdeliver greater tension when the system demands and less tension whenless tension is required. This can result in increased bearing life inbelt driven accessories, reduced belt slippage under heavy loadingconditions, and an increased effective life of the tensioner 22 itself.

While one form of fluid dampening means 40 for the tensioner 22 of thisinvention has been illustrated and described, it is to be understoodthat other fluid dampening means can be utilized for the tensioner 22 ofthis invention, as desired.

For example, another belt tensioner of this invention is generallyindicated by the reference numeral 22A in FIG. 8 and parts thereofsimilar to the tensioner 22 previously described are indicated by likereference numerals followed by the reference letter "A."

As illustrated in FIG. 8, the tensioner 22A is substantially identicalto the tensioner 22 previously described except that the fluid dampeningmeans 40A thereof comprises a substantially conventional shock absorberstructure having a first tubular member 135 telescoped in sliding andsealing relation within an open end 136 of another tubular member 137, aclosed end 138 of the tubular member 135 being secured to the plate 48Aof the belt engaging means 38A while a closed end 139 of the tubularmember 137 is secured to the top plate 58A of the support member 44A soas to be interconnected to the support means 36A.

In particular, the closed end 138 of the tubular member 135 is securedto the plate 48A by a fastening means 140 being disposed in the opening113A of the plate 48A and being held thereto by the nut 114A, thefastening means 140 being secured in an opening 141 in the closed end138 of the tubular member 135 in any suitable manner.

The closed end 139 of the tubular member 137 has a fastening means 142carried thereby and being received in an opening 143 passing through thetop wall 58A of the support means 44A and being secured thereto by asuitable nut 144.

The fastening means 142 also includes a piston-like rod 145 beingsuspended within an open end 146 of the tubular member 135 and carryinga piston means 147 on the lower end 148 thereof so that the piston means147 is held stationary by the support means 44A while the tubular member135 is adapted to slide relative to the piston means 147.

The piston means 147 divdies the tubular member 135 into two chambersections 149 and 150, the piston member 147 having a plurality ofopenings 151 passing therethrough to fluidly interconnect the chambers149 and 150 together.

However, a movable valve member 152 is carried on a reduced sleeveportion 153 of the end 148 of the rod 145 so that the valve member 152can be disposed against a lower shoulder 154 of the rod 148 and therebybe disposed away from some of the passage 151 of the piston member 147while being adapted to move upwardly on the sleeve portion 153 to engageagainst the piston member 147 and close off one or more of the passages151 in a manner and for a purpose hereinafter described.

A suitable hydraulic fluid, such as a hydraulic oil 155, is disposed inthe chambers 149 and 150 and in the embodiment illustrated in FIG. 8,the chamber 150 is only filled to a level 156 in order to compensate forthe amount of volume being taken up by the open end 146 of the tubularmember 135 telescoping upwardly into the tubular member 137 as will beapparent hereinafter.

Therefore, it can be seen that it is a relatively simple method of thisinvention to make the tensioner 22A in the manner previously describedin connection with the tensioner 22 and merely substitute the shockabsorber means 40A for the fluid dampening means 40 thereof to operatein a manner now to be described.

After the support means 36A has been mounted to the engine bracket 37 inthe manner previously described and the initial compression force of thecompression springs 39A have been set in the manner previously describedfor the tensioner 22, any downward movement of the belt engaging means38A under the force of the compression springs 79A causes the tubularmember 135 to move downwardly relative to the tubular member 137 andthereby increase the volume of the chamber 149 so that a resultingvacuum condition in the chamber 149 immediately draws fluid from thechamber 150 through the openings 151. The openings 151 are so sized thatthe same provide a desired dampening to such downward movement of thebelt engaging means 38A. Of course, the openings 151 can be so designedthat there will be no restriction of such downward movement of the beltengaging means 38A under the force of the compression springs 79A ifdesired.

Conversely, when the engaged belt tends to move the belt engaging means38A upwardly in FIG. 8, such upward movement of the tubular member 135relative to the tubular member 137 tends to cause a decrease in thevolume of the chamber 149 so that the fluid 155 therein is forcedthrough the openings 151 into the chamber 150. However, such upward flowof the fluid 155 relative to the stationary piston 147 causes the valvemember 152 to move upwardly and close off one or more of the passages151 so that the fluid flow through the piston member 147 from thechamber 149 to the chamber 150 is restricted to thereby restrict upwardmovement of the belt engaging means 38A at a rate greater than when thebelt engaging means 38A is moved downwardly for the reasons previouslyset forth in connection with the tensioner 22.

Therefore, it can be seen that the shock absorber means 40A is disposedin a parallel relation between the parallel springs 79A to render thetensioner 22A relatively small and compact in the same manner that thepiston and cylinder means 84, 85 is disposed in a parallel relation tothe springs 79 to render the tensioner 22 relatively small and compact,the shock absorber means 40A and piston and cylinder means 84, 85 eachfunctioning to fluid dampen movement of the respective belt engagingmeans 38A and 38 relative to the respective support means 36A and 36.

Another belt tensioner of this invention is generally indicated by thereference numeral 22B in FIGS. 9-12 and parts thereof similar to thetensioners 22 and 22A previously described are indicated by likereference numerals followed by the reference letter "B".

As illustrated in FIGS. 9 and 10, the tensioner 22B is essentially thesame as the tensioner 22 previously described except that the sameutilizes another fluid dampening means of this invention that isgenerally indicated by the reference numeral 40B and comprises an outerring-like member 157 and an inner ring-like member 158 disposed in theouter ring member 157 with the ring members 157 and 158 being arrangedfor relative rotational movement therebetween whereby the fluiddampening means 40B comprises a rotary dampening means.

In particular, the ring-like member 157 is substantially cylindricalwith an inner peripheral cylindrical surface 159 and a rear wall 160cooperates with a closure or front wall member 161 to define a chamber162 within the ring-like member 157.

The inner ring-like member 168 comprises a substantially cylindricalmember having an outer peripheral cylindrical surface 163 adapted toface the internal peripheral surface 159 of the outer ring member 157and is mounted on a central shaft 164 that has one end 165 journaled ina closed ended bore 166 in the cover member 161 and another end 167 thatpasses through an opening 168 in the rear wall 160 of the outer ringmember 157.

The rear wall 160 of the outer ring member 157 is adapted to be securedto the rear wall 52B of the support member 44B of the tensioner 22B inany suitable manner, such as by welding or the like, with the shaft 164of the dampening means 40B passing through an opening 169 in the rearwall 52B while being rotatable therein.

The end 167 of the shaft 164 carries a pinion gear 170 that has its gearteeth 170' adapted to be disposed in meshing engagement with teeth 171of a rack-like member 172 secured to the transverse wall 48B of the beltengaging means 38B of the tensioner 22B. For example, the rack-likemember 172 can have an externally reduced rod-like part 173 passingthrough the opening 113B in the wall 48B to be secured thereto by thenut 114B whereby the rack-like part 172 of the fluid dampening means 40Bis mounted in parallel relation between the parallel springs 79B andthereby permits the up and down movement of the wall 48B to betranslated into rotary movement of the shaft 164 and, thus, rotarymovement of the inner ring-like member 158 relative to the outerring-like member 157 for a purpose hereinafter described.

The inner ring-like member 158 has a plurality of circumferentiallyspaced and radially outwardly extending vanes 174 having free ends 175disposed closely adjacent the internal peripheral surface 159 of theouter ring-like member 157 for a purpose hereinafter-described.

Similarly, the outer ring-like member 157 has a plurality ofcircumferentially spaced and radially outwardly extending vanes 176respectively provided with free ends 177 disposed closely adjacent theouter peripheral surface 163 of the inner ring-like member 158 for apurpose hereinafter described, the vanes 176 of the outer ring-likemember 157 and the vanes 174 of the inner ring-like member 158 beingdisposed in the staggered relation illustrated in FIG. 11 to permitlimited rotary movement of the inner ring-like member 158 in both aclockwise and counter clockwise direction until the vanes 174 abutagainst the vanes 176 as will be apparent because the vanes 176 aredisposed in the rotary path of movement of the vanes 174.

By disposing a suitable dampening fluid in the chamber 162 of the rotarydampening means 40B, such as a hydraulic oil or the like, the rotarymovement of the inner ring-like member 158 relative to the outerring-like member 157 can be controlled by the degree of spacing providedbetween the outer free ends 175 and 177 of the vanes 174 and 176 and thecooperating peripheral surfaces 159 and 163 of the ring-like members 157and 158 as will be apparent hereinafter.

Also, the amount of fluid dampening in the direction of rotation of theinner ring-like member 158 relative to the outer ring-like member 157can be preferentially controlled by changing the angle of attack of oneside 178 or 179 of the vanes 174 relative to the other side 179 or 178thereof and/or the angle of attack of one side 180 or 181 of the vanes176 relative to the other side 181 or 180 thereof. In addition oralternately thereto, the vanes 174 and/or vanes 176 can be provided withone-way check valves in passages passing through the opposed sides 178and 179 thereof to permit unrestricted flow in one directiontherethrough and restricted flow in the other direction therethrough aswill be apparent hereinafter.

In any event, when the desired dampening fluid, such as a hydraulic oilor the like is disposed within the chamber 162, the dampener 40B willdampen up and down movement of the belt engaging means 38B of thetensioner 22B through rotary movement of the inner ring-like member 158.

Therefore, it can be seen that it is a relatively simple method of thisinvention to form the tensioner 22B in the manner previously describedand to utilize the rotary dampener 40B of this invention therewith tooperate in a manner now to be described.

After the tensioner 22B has been mounted to the mounting bracket 37 ofthe engine 20 and the force of the springs 79B has been set in themanner previously described for the tensioner 22, subsequent downwardmovement of the belt engaging means 38B under the force of thecompression springs 79B in a belt tensioning direction causes therack-like member 172 to move downwardly therewith and thereby rotate thepinion gear 170 in a counterclockwise direction in FIG. 9 to causecounterclockwise rotation of the shaft 164 and, thus, counterclockwiserotation of the inner ring-like member 148 relative to the outerring-like member 157 in FIG. 11 whereby the inner vanes 174 tend todrive the fluid against the sides 179 thereof toward the sides 180 ofthe outer vanes 176 and thereby cause the hydraulic fluid in thecollapsing pockets between the vanes 174 and 176 to be forced betweenthe free ends 177 of the vanes 176 and the inner peripheral surface 163of the inner ring-like member 58 as well as through the spacing betweenthe free ends 175 of the inner vanes 174 and the inner peripheralsurface 159 of the outer ring-like member 157 in a manner to retard orrestrict such downward movement of the belt engaging means 38B for thedampening reasons previously set forth.

Conversely, when the tensioned belt tends to move the belt engagingmeans 38B upwardly in FIGS. 9 and 10, such upward movement of thetransverse wall 48B carries the rack-like member 172 therewith andcauses the pinion gear 170 to rotate in a clockwise direction in FIG. 9and thereby cause clockwise rotation of the inner ring-like member 158relative to the outer ring-like member 157 so that the inner vanes 174have the sides 178 thereof tending to compress the fluid toward thesides 181 of the outer vanes 176. Thus, the fluid in the collapsingpockets of the dampener 40B is forced through the space between theinner free ends 177 of the outer vanes 176 and the inner peripheralsurface 163 of the inner ring-like member 158 as well as between theouter free ends 175 of the inner vanes 174 and the inner peripheralsurface 159 of the outer ring member 157 to restrict such rotarymovement and thereby dampen the upward movement of the belt engagingmeans 38B relative to the support means 36B.

As previously set forth, by making the rotary motion of the dampener 158more restrictive in the clockwise rotation thereof in FIG. 11 than inthe counterclockwise rotation thereof, a greater restrictive force willbe imposed on the belt engaging means 38B in a direction thereof awayfrom the belt than toward the belt for the reasons previously set forth.

While the rotary dampening means 40B of this invention has beenillustrated and described as being particularly adapted to provide afluid dampening means for the tensioner 22B it is to be understood thatthe rotary dampener 40B of this invention can be utilized for dampeningother devices than belt tensioners as desired whereby the fluiddampening device 40B of this invention is not to be limited to only abelt tensioner arrangement.

Therefore, it can be seen that this invention not only provides improvedbelt tensioners and methods of making the same, but also this inventionprovides improved parts for such belt tensioners or the like and methodsof making such improved parts.

While the forms and methods of this invention now preferred have beenillustrated and described as required by the Patent Statute, it is to beunderstood that other forms and method steps can be utilized and stillfall within the scope of the appended claims.

What is claimed is:
 1. In a tensioner for a power transmission belt thatis adapted to be operated in an endless path, said tensioner comprisinga support means for being fixed relative to said belt, a belt engagingmeans carried by said support means and being movable relative thereto,mechanical spring means operatively associated with said support meansand said belt engaging means for urging said belt engaging meansrelative to said support means and against said belt with a force totension said belt, and fluid dampening means operatively associated withsaid support means and said belt engaging means to dampen the movementof said belt engaging means relative to said support means in at leastone direction of movement thereof, said fluid dampening means comprisinga piston and cylinder means having a piston member and a cylindermember, the improvement wherein said mechanical spring means comprises apair of coiled compression springs with their longitudinal axes disposedin substantially parallel side-by-side spaced relation, said fluiddampening means being generally disposed between said springs and insubstantially parallel relation therewith, said belt engaging meanshaving a part thereof disposed in sliding relation with said supportmeans, said part of said belt engaging means having a pair ofsubstantially flat parallel spaced apart surfaces interconnectedtogether by a front wall, said support means having a part thereofcomprising a pair of substantially flat parallel spaced apart surfacesrespectively facing said surfaces of said part of said belt engagingmeans and being interconnected together by a rear wall, and bearingmeans disposed between said facing surfaces to facilitate said slidingmovement between said part of said belt engaging means and said supportmeans, said part of said belt engaging means having a thirdsubstantially flat surface disposed between said pair of surfacesthereof and being substantially transverse relative thereto, saidsprings and said piston member of said fluid dampening means beingrespectively operatively interconnected to said third surface of saidbelt engaging means, said part of said support means having a thirdsubstantially flat surface disposed between said pair of surfacesthereof and being substantially transverse thereto and being betweensaid pair of springs, said cylinder member of said fluid dampening meansbeing operatively interconnected to said third surface of said supportmeans.
 2. A tensioner as set forth in claim 1 wherein said cylindermember has an externally threaded portion, said third surface of saidsupport means having an internally threaded opening passing therethroughand threadedly receiving said threaded portion of said cylinder membertherein to operatively interconnect said cylinder member to said supportmeans.
 3. A tensioner as set forth in claim 1 wherein said springs eachhas opposed ends, each said spring having one of said ends thereofbearing against said third surface of said belt engaging means andhaving the other of said ends thereof bearing against said supportmeans.
 4. A tensioner as set forth in claim 3 wherein said support meanshas a pair of adjustable parts against which said other ends of saidsprings respectively bear whereby the urging force of said springs isadjustable.